Snap action electric switch



Feb. 24, 1970 H. JAKoBs SNAP ACTION ELECTRIC SWITCH 2 Sheets-Sheet 1 Filed Nov. 25, 1966 @4 16 .auf MVM MM m @u .ww m w 4.

Feb. 24, 1970 H. JAKoBs SNAP ACTION ELECTRIC SWITCH Filed NOV. 25, 1966 2 Sheets-Sheet 2 United States Patent O 3,497,839 SNAP ACTION ELECTRIC SWITCH Hans Jakobs, Schaumburg Township, Cook County, Ill.,

assignor to C. E. Niehol & Co., Chicago, Ill., a corpol ration of Illinois Filed Nov. 25, 1966, Ser. No. 597,045 Int. Cl. H01h 61/04 U.S. Cl. 337-89 14 Claims ABSTRACT F THE DISCLOSURE A thermally operated snap action electric switch for intermittent energization of signal lights or the like includes a generally flat and not inherently stressed resil ient met-al vane, together with a pair of biasing straps separate from the vane and attached to opposite ends of the vane for flexing the vane in one direction transversely of the bias and away from the biasing straps. An expansible pull wire overlies the opposite surface of the vane and has at least one end attached to the vane and the other end fixed with respect to the support for the vane. The pull wire in its unexpanded or contracted condition has a length such that it is effective to flex the vane in the opposite direction transversely to the bias. As the pull wire is expanded from its contracted condition, the vane snaps with an over-center movement to its alternate position under the inuence of the biasing straps. As the pull wire subsequently contracts to its unexpanded condition, the vane again snaps with an over-center movement to its initial position. Heating means are provided for con trolling the expansion and contraction of the pull wire, and suitable switch contacts are associated with the vane.

The present invention relates to snap action electric switches of the type customarily used to provide an intermittent of periodic energization of signal lights, such as those used in automobile turn signals.

A further object of the present invention is to provide a switch capable of being made readily and economically and utilizing an unstressed resilient metallic vane requiring no heat treatment and of a construction which can readily be modified to compensate for differences in the physical properties of the vane material.

A further object of the present invention is to provide a snap device including a substantially Hat resilient vane and biasing means at one side of and att-ached to opposite ends of the vane to flex the vane in one direction transversely of the bias, whereby the magnitude of the bias may be readily adjusted, as during manufacture, by bend ing the vane -at the points of attachment of the biasing means thereto.

A further object of the present invention is to provide a temperature compensated device having a uniform flash rate and, more particularly, a device including a resilient vane and biasing means that `are made of different materials and in which the biasing means has a higher co efiicient of temperature expansion than the vane, whereby the device inherently operates at a slower rate at decreased temperatures, thereby to offset the increase in operating voltage normally provided by the voltage regulator of an automobile at colder temperatures.

In brief, the apparatus of the present invention com prises a substantially flat resilient metallic vane, and bias ing means separate from the vane and overlying one sur face of the vane. The biasing means is attached to op posite ends of the vane and flexes the vane in one direc tion transversely of the bias and away from the biasing means. Expansible pull means overlies the other surface of the vane and has at least one end attached to the vane and has -a length such that in its unexpanded, or contracted condition it flexes the vane in a second opposite direction transversely to the bias and over-center toward the biasing means. The biasing means and expansible pull means are arranged so that in response to alternate expansion and contraction of the pull means there re sults a snap action, over-center movement of the vane between positions in which the vane is alternately liexed in the first and second directions.

The vane is mounted on a supporting base provided with one or more fixed contacts arranged for cooperation with one or more contacts carried on the vane. Heating means associated with the expansible pull means is alternately energized and deenergized to effect the movement of the vane between its two positions. The biasing means and vane are made of different materials with the pull means having a higher coefficient of thermal expansion than the vane, thereby to provide a more uniform fre quency of operation with varying temperatures.

The vane conveniently may be octagonal in shape and a pull wire is attached to opposite points of the vane. The biasing means is constituted by a pair of straps secured to the vane and overlying the opposite surface of the vane. The straps are secured to points of the vane adjacent the points to which the pull wire is secured, and are parallel to the pull Wire.

The vane is provided with slots extending from the edges toward the center of the vane transversely of the biasing straps and pull wire. These slots limit the flexing of the vane to a relatively small area near the center of the vane and allow the vane to be adjusted for differences in the vane material. Since flexing occurs only near the center of the vane, a secure, wide-area mount may be used.

Adjustment of the magnitude of bias exerted by the straps can readily be accomplished by bending the points at which they are secured to the Vane, and the length of the slots can readily be varied to compensate for differences in the physical properties of the material of the vane. The vane has no inherent, intrinsic or built-in biasing or deformation, and construction is simplified by elimination of a heat treatment operation heretofore generally required. The elimination of the vane deformation also provides a more uniform device and simplifies production.

In an alternative embodiment of the invention, the pull wire has one end attached to the supporting structure.

VOther objects and advantages of the present invention will become apparent from the ensuing description of ern- !bodiments thereof, in the course of which reference is had to the accompanying drawings, in which:

FIG. 1 is a perspective view of a snap action switch device embodying the features of the invention, viewed from one side;

FIG. 2 is a perspective view of the device of FIG. l, viewed from the opposite side;

FIG. 3 is a plan view of the vane utilized in the device of FIG. l;

FIG. 4 is a sectional view along the line 4 4 of FIG. 3;

FIG. 5 is a plan view of the vane with the biasing means attached;

FIG. 6 is a sectional view along the line =6-6 of FIG. 5;

FIG. 7 is a plan view of the Vane with -both the pull wire and the biasing means attached;

FIG. 8 is a sectional view along the line 8 8 of FIG. 7 illustrating the position of the vane when the pull wire is in the unexpanded, or contracted condition;

FIG. 9 is a view similar to FIG. 8 illustrating the position of the van when the pull wire is in the expanded condition;

FIG. is a perspective view of an alternative embodiment of the invention, viewed from one side;

FIG. 11 is a perspective view of the device of FIG. l0, viewed from the opposite side;

FIG. 12 is a plan view of the vane used in the device of FIG. 10 with the biasing means and the pull means attached;

FIG. 13 is a sectional view along the line 13-13 of FIG. 12 illustrating the position of the vane when the pull wire is in the unexpanded, or contracted condition; and

FIG. 14 is a view similar to FIG. 13 showing the position of the vane when the pull wire is in the expanded condition.

In FIGS. 6, 8, 9, 13 and 14, the showings of the vaneS are somewhat exaggerated and simplified for purposes of illustration, and the actual shapes may be somewhat more complex.

Referring now to the drawings, and initially to FIGS. 1-9, there is illustrated a snap action electric switch device generally designated as 10 embodying the features of the present invention and including a at, unstressed, metallic vane 12. O'verlying one surface of the vane 12 are biasing means which in the illustrated embodiment of the invention comprise a pair of biasing straps 14 attached to opposite ends of the vane 12. The straps 14 flex the vane in one direction away from the straps 14. In order to control the position of the vane 12, pull means comprising an expansible pull wire 16 is attached to the vane 12 and overlies the opposite surface of the vane. The length of the pull wire is such that in its contracted, unexpanded condition the pull wire 16 exes the vane in the opposite direction toward the biasing straps 14. The biasing straps 14 and the pull wire 16 are effective in response to expansion and contraction of the pull wire 16 to move the vane 12 between its alternate iiexed positions.

The vane 12, in accordance with the invention, is not stressed, creased, bent, or otherwise deformed, but rather is formed of a flat, unstressed, metallic material. Thus in order to form the vane 12, it is necessary merely to stamp it or otherwise cut it from a fiat sheet of metal. Construction of the vane is simplified because it is unnecessary to heat treat the vane to relieve material stresses such as are induced by deformation of many prior art vanes.

As illustrated most clearly in FIGS. 3, S and 7, the vane 12 is octagonal in shape. In construction of the device 10, the biasing straps 14 are attached to spaced alternate points 12a of the vane 12 and extend parallel to one another (FIGS. 5 and 6). The biasing straps 14 overlie one surface of the vane 142. The biasing straps 14 comprise strips of material, preferably metallic, having a length somewhat longer than the distance between the points 12a. Ends 14a of each biasing strap 14 are crimped over the points 12a and are spot welded in place.

As appears most clearly in FIG. 6, the elfective length of the biasing straps 14 is such as to flex the vane 12 away from the biasing straps 14 and transversely of the direction of bias. rIl`he effective length of the straps 14, and thus the magnitude of the bias applied to the vane 12, can be conveniently and easily adjusted by bending the points 12a of the vane 12. 'Due to the fact that each end 14a of each biasing strap 14 is attached to a different point 12a, the bias of each strap 14 may be adjusted independently of the other strap and independently of the pull wire 16.

The pull wire 16 overlies the surface of the vane 12 opposite the biasing straps 1-4 (FIGS. 7-9), and is attached between opposed points 12b of the vane 12. The pull wire 16 comprises a strip of preferably metallic heat expansible material having an overall length slightly in excess of the distance between the points 12b. In order to attach the pull Wire 16 to the vane 12, end portions 16a of the pull wire 16 are crimped over the points 12b and spot welded in place.

The contracted, or unexpanded effective length of the pull wire 16 is such as to flex the vane 12 in a second direction toward the biasing strap 14 and transversely of the bias (FIG. 8). The effective length of the pull wire 16 in its contracted, or unexpanded condition can be adjusted -by bending the points 12b a desired amount.

In operation the vane 12 moves with a snap action between its two positions. lOne position is that illustrated in FIG. 8 wherein the pull wire 16 is in its contracted, or unexpanded condition. When the pull wire is heated, it expands and allows the vane 12 to move with a snap action to its alternate position illustrated in FIG. 9. When the pull wire subsequently cools, the vane 12 returns with a snap action to the position illustrated in FIG. 8.

In order to control the stiffness of the vane 12, and to restrict the flexing of the vane to a relatively small and well-defined area of the vane surface, the vane is provided with a pair of opposed slots 18. The slots 18 extend from opposed edges of the vane toward the center of the vane in a direction transverse to the biasing straps 1,4 and the pull wire 16. Because of the slots 18, the flexing of the vane 12 is limited to a region at the center of the vane between the innermost ends of the slots 18. As a result, the vane 12 does not assume a continuous curved or bow-like conguration but rather flexes into a shallow V shape, as shown in FIGS. 8 and 9.

In addition, the length of the slots 18 determines the stiffness, or opposition to ilexing provided by the vane 12. Therefore, in construction of the device 10, the lengths of the slots 18 can be varied to compensate for differences n the material of which the vane 12 is fabricated. For example, if the material of the vane 12 is stilf because of excess thickness or other reasons, the slots 18 may be made longer to achieve the desired degree of flexibility. Conversely, if the material of the vanes 12 is more resilient, the slots 18 may be made shorter.

Referring now to FIGS. 1 and 2, the device 10 includes a base 20 preferably formed of nonconductive material such as molded plastic. The device may also include a cover (not shown) engageable with the base 20 to protect the vane 12 and associated elements. Extending downwardly from the base 20 are three plugin type terminal members 22, 24 and 26. Extending upwardly from the surface of the base 20 are three supports 28, 30 and 32, each electrically connected to one of the treminal members 22, 24 and 26 by means of a conductive rivet 34. The rivets 314 serve to mount the terminals and supports to the base 20, and the base is provided with positioning abutments 20u for aligning the supports 28, 30 and 32 in proper position.

Because the flexing of the vane 12 is restricted to a relatively small region near the center of the vane 12, a large portion of the surface of the vane 12 may be used firmly to mount the vane. Accordingly, the support 28 includes a relatively large-area portion which may be in face-toface abutment with a large part of the bottom of the vane 12. If desired, the vane may be spot welded at one or several points to the support 28 to assure that the vane is securely held against the mechanical shocks and vibrations to which it may be subjected if the device 10 is used in an automobile.

Because the bottom or a substantial part of the bottom portion of the vane 12 is fixed with respect to the base 20, the upper portion of the vane 12 moves back and forth during operation of the device 10. A pair of contacts 36 and 38 are carried on opposite surfaces of the vane near its uppermost edge. A pair of fixed contacts 40 and 42 are supported respectively by the supports 30 and 32 and are engageable respectively with the contacts 36 and 38 in the alternate positions of the vane 12. Contacts 40 and 42 also act as stops to limit Imovement of the vane, and also produce a desirable clicking noise in operation.

Alternate heating and cooling of the pull wire 16 in order alternately to expand and contract the pull wire may be accomplished in any desirable manner. In the illustrated device 10, the pull wire 16 is heated indirectly by means of a resistance heating wire 44 disposed in intimate heat transfer relation with the pull wire 16. More specifically, the wire 44 extends between a pair of conduc-tive connecting member 46 and 48 welded respectively to the rivets 34 connected to the terminals 22 and 26. A loop of the wire 44 is in heat transfer relation with La central portion 16b of the pull Wire 16. The wire 44 is quite flexible and is covered with insulation,

Many uses for the device will be apparent to those skilled in the art. In particular, one use for the device 10 is to control the flashing signals of automobile turn indicating apparatus. In one circuit suitable for this use, one terminal of the automobile battery is connected to the terminal 22, and the terminals 24 and 26 are coupled to the other battery terminal, both of these terminals being connected to the battery through suitable turn signal indicating lamps.

In operation, the vane 12 is normally in the condition illustrated in FIGS. l, 2 and 8 wherein the pull wire 16 is in itscontracted, or unexpanded condition. In this condition the vane is flexed in the direction toward the biasing straps 14 and the contacts 36 and 40 are in engagement and complete a circuit between the terminals 22 and 2.4. To initiate operation, a suitable operating switch is lused to complete a circuit from one side of the battery to the terminal 22, through the support 28 and vane 12 to the contact 36, through the contact 40,

the support 30, the terminal 24, and to the other sideA of the battery through an indicating lamp or lamps, initially energized. The resistance wire 44 is connected across the terminals 22 and 26 and heats the pull wire 16. The high resistance of the wire 44 prevents energization of the indicating lamps associated with the terminal 26.

After the pull wire 16 is heated for a period of time, it expands to the point when thevvane 12 is permitted to snap to its alternate position as shown in FIG. 9. This lmovement causes the contacts 36 and 40` abruptly to open and the contacts 38 and 42 abruptly to close. In this condition a circuit is completed from one side of the battery to terminal 22, support 28, vane 12, contact 38, contact `42, support 32, terminal 26 and to the other side of the battery through other indicating lamps. In this condition the closed contacts 38 and 42 shunt the wire 44 thus substantially decreasing or eliminating current flow through the wire 44. As a result, the pull wire 16 begins to cool, and after a period of time contraction of the pull wire 16 snaps the vane to its original condition. This operation is continued resulting in alternating operation of the signal lamps until such time as the operating switch is opened.

The rate of operation of the snap action switch device 10 is obviously dependent upon many features of its physical construction, such as the resilience of the vane, the magnitude of the bias, the resistance of wire 44, etc. However, for a given device 10i, the rate of operation should desirably be as constant as possible throughout a'll operating temperatures to which the device 10 might be subjected.

Automobile electric systems customarily include a temperature compensated voltage regulating arrangement which increases the applied battery voltage as temperature decreases. An increased battery voltage has the effect of decreasing the time required for the wire 44 to heat the pull wire 16. Accordingly, in prior art devices, the rate of operation of the device has increased in colder temperature.

In accordance with a feature of the present invention, the device 10 is compensated against temperature changes to assure that the device operates at a substantially uniform rate of speed regardless of the temperature. Accordingly, the biasing straps 14 are made of a different material than that used for the vane 12. Specifically, the

biasing straps 14 have a higher coefcient of expansion than the vane 12. As a result, the magnitude of the biasing force is increased as the temperature decreases since the biasing straps 14 contract more than does the vane 12 upon a decrease in temperature. This increase in the magnitude of the bias serves to slow down the operation and to compensate for the voltage increase imposed by the voltage regulator.

Having reference now to FIGS. 1()-l4, there is illustrated a snap action switch device generally designated as 50 and comprising an alternative embodiment of the present invention. Since the device 50 and the device 10 described above have some common features of construction, similar reference numerals are used to designate similar elements of both devices.

The device 50 includes a vane 52 similar to the vane 12 described above except that it is weakened, as by a central aperture 54 formed in the vane between the ends of the slots 16. As explained above, the slots 16 limit the flexing of the vane to the area between the slots 16. The weakening aperture 54 serves to soften the vane so that it is less resistant to flexing.

Biasing straps `14 are attached to points 52a of the vane 52 in the manner described above to flex the vane in one direction away from the straps 14. A pull wire 56 has one end 56a attached to a point 52b of the vane in the manner described above. The other end 56b of the pull wire is fixed to the base, as described below, in order, when contracted, to flex the vane 52 in the other direction toward the biasing straps 14 (FIG. 14).

The base 20 of the device includes a pair of terminals `58 and 60, and a pair of support members 62 and 64 connected by rivets 34 to the terminals 58 and 60. An additional support 66 is mounted to the base 20 by a rivet 34 and is not connected to a terminal. The support 66 is used to support the vane 52, and includes a wide-area portion engaging the bottom portion of the vane 52, as well as a stop 66a limiting movement of the vane 52 in one direction. The bottom of vane 52 may be spot welded at several points to the support 66 to ensure firm mounting.

The pull wire 56 is directly, rather than indirectly, heated, and the end 5611 thereof is connected to the support 62 under tension, and is spaced from the bottom of the vane 52, as shown in FIGS. 13 and 14. The pull wire 56 has an effective length such as normally to flex the vane 52 to the position shown in FIG. 13 when the pull wire is in the contracted, or unexpanded condition. In this condition, a contact 68 on the vane engages a xed contact 70 carried by the support 64, which also serves as a stop.

When the device 50 is used to control an automobile turn indicator lamp or lamps, a circuit including the battery and the lamps to be controlled is connected between the terminals 58 and 60. To initiate operation, a control switch in this circuit is closed and current ows from the terminal 58 through support 62, through the pull wire 56 to the vane 52, through the closed contacts 68 and 70, support 64 and terminal 60 to energize the lamps. Current owing through the pull wire 56 heats and causes expansion of the wire.

After a period of time, the wire 56 expands enough to allow the vane 52 to snap to the alternate position shown in FIG. 14, thereby to open the contacts 68 and 70. This deenergizes the signal lamps and current stops ilowing through the pull wire, causing it to cool. After a period of time, the pull Wire 56 contracts and snaps the vane back to its original position. This operation continues and causes the signal lamps intermittently to be energized until such time as the control switch is opened.

Temperature compensation of the device 50 is accomplished in the manner described above by forming the biasing straps 14 of a material having a higher coeiiicient of expansion than the material used for the vane 52. In addition, it will be appreciated that many other ad- 7 vantages realized in the device 10 are achieved also with the device 50.

Although various different materials could be used in the fabrication of the devices 10 and 50, in devices constructed in accordance with the invention the vanes have been made of carbon spring steel having thicknesses in the approximate range of six to seven thousandths of an inch. The pull wires and the biasing straps can be -made of various high nickel content, nickel chromium alloys, such as Iconel X. The invention, of course, is not limited to the use of any particular materials.

While the present invention has 'been described in connection with the details of particular illustrated embodiments thereof, it should be understood that the present invention is not limited to these details, except insofar as set forth in the accompanying claims. As one example, the device 10 can be used as a two terminal device rather than a three terminal device as illustrated. Thus, the terminal 24 can be omitted or not used and the fixed contact 40 used only as a stop for the vane 12. The circuit to be controlled is then connected between the terminals 22 and 26 and provides a simple ashing signal rather than an alternating signal.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

'1. In apparatus of the type described:

an unstressed resilient metallic vane;

biasing means separate from the vane and overlying one surface of the vane; said biasing means including a pair of narrow, elongated, flexible biasing straps mounted in tension on said vane and having opposite ends attached directly to the edge of the vane at opposite ends of the vane; said biasing means being effective to flex the vane to a rst position in which the vane is flexed in one direction transversely to the bias and away from the Ibiasing means;

and expansible pull means overlying the other surface of the vane and having at least one end attached directly to the edge of said vane at one of said opposite ends of the vane;

said pull means having a length such that in its unexpanded or contracted condition it overcomes the tension effect of said biasing means and flexes the vane from said first position to a second position in which the vane is flexed in a second and opposite direction transversely to the 4bias and over-center toward the biasing means;

the biasing means and expansible pull means effecting in response to alternate expansion and contraction of only the pull means a snap over-center movement of the vane between said two positions in which the vane is alternately flexed in said lirst and second directions.

2. Apparatus as claimed in claim 1, including supporting means attached to a first of said opposite ends of the vane, said pull means comprising a thermally expansible wire having one end relatively xed with respect to said supporting means and another end attached t the second of said opposite ends of the vane.

3. Apparatus as claimed in claim 2, said wire being attached to both said iirst and second ends of the vane.

4. Apparatus as claimed in claim 2, said one end of said wire being attached to said supporting means.

5. Apparatus as claimed in claim 1 wherein said biasing straps are made of a material different from that of the vane and having a higher thermal coefficient of expansion than the vane.

6. Apparatus as claimed in claim 1 wherein said vane is of a shape having three points near each of said opposite ends of the vane.

7. Apparatus as claimed in claim 1, said vane being octagonal in shape.

8. Apparatus as claimed in claim 7 wherein said pull means is secured to opposite points of the vane, and said biasing means comprises a par of straps secured to the points adjacent the opposite points.

9. The apparatus of claim 1 wherein said Vane has substantial width in a direction transverse to said biasing strip, a slot in said vane extending from a side edge of the vane a substantial distance toward the center of the vane, said slot extending transversely to and intersecting one of said biasing straps.

10. The apparatus of claim 9, a second slot in said vane extending inwardly from the opposite side edge of the vane a substantial distance toward the center of the vane, said second slot intersecting the other of said biasing straps.

11. Apparatus as claimed in claim 10, said vane having an aperture between said slots.

12. In apparatus of the type described, an unstressed resilient metallic vane, biasing means separate from the vane overlying one surface of the vane and attached to opposite ends of the vane to ex the vane to a first position in which the vane is exed in one direction transversely to the bias and away from the biasing means, expansible pull means overlying the other surface of the vane and having at least one end attached to one of said opposite ends 0f the Avane, said pull means having a length such that in its unexpanded or contracted condition it lexes the vane from said iirst position to a second position in which the vane is exed in a second and opposite direction transversely to the bias and over-center toward the biasing means, the biasing means and expansible pull means effecting in response to alternate expansion and contraction of only the pull means a snap over-center movement of the vane between said two positions in which the vane is alternately flexed in said iirst and second directions, said vane having slots extending from the sides toward the center of the vane and transversely of the direction of the bias, said slots being located substantially midway between said opposite ends of the vane, supporting meansy secured to the vane intermediate the slots and one end of the vane, a base for the mounting means, a vane contact carried by the other end of the vane, and fixed contact structure mounted on the base and located so as to be engaged by the vane contact in one of said two positions, said biasing means including parallel straps spaced from each other and intersecting the central portions of the slots.

' 13. Apparatus as claimed in claim 12 wherein said expansible pull means is a thermally expansible wire disposed between said straps.

14. Apparatus as claimed in claim 13 wherein the biasing straps are made of a material having a higher coeflicient of thermal expansion than the vane.

References Cited UNITED STATES PATENTS 2,537,485 1/1951 Sitzer et al.' 337--135 2,166,238 7/ 1939 Davis.

2,299,767 10/ 1942 Schmidinger.

3,174,013 3/ 1965 Siiberg.

BERNARD A. GILHEANY, Primary Examiner R. L. COHRS, Assistant Examiner U.S. Cl. X.R. 337-135, 

